Upset..

Yesterday, we receive an email from our client, the content of the email basically mentioned that he doesn't satisfy our work and what we are doing.
Today, we fortually see our supervisor, he asked us after reading the email:"Did you guys feel upset about this email, don't need to feel upset." Our team leader then answer not really feel upset. But in fact for me, at that moment, i really feel upset about that, i was quite lose when i read the email, because I really put effort on the work and I spent more time in this project compare with my other 3 subjects. I think not even me, my teamates also did their best, but i don't know why.
I remember in our second meeting, I did summaries three points of the system we should follow, and he also agree that, but i don't know why.
Anyway, we have our own discussion today about few ways to improve. And we fastly separate several areas for the system for each memeber, then we can move on earlier.